Disc brakes, for example air actuated disc brakes are commonly used for braking heavy vehicles such as trucks, buses and coaches. There are many types of disc brakes available. An example of one of the many types of pneumatic disc brakes is shown in FIG. 1.
Referring to FIG. 1, the disc brake 110 has a carrier 112 that carries a caliper 114. The carrier also carries friction elements 122 such that one friction element is positioned on each side of a rotor 116 of the disc brake 110. An air actuator is provided for moving an inboard friction element into frictional contact with the rotor 116 via an actuator mechanism (not shown). The rotor 116 is fixed in an inboard-outboard direction, so that when the inboard friction element is pushed towards and contacts the rotor 116, further pushing of the inboard friction element towards the rotor 116 causes the caliper 114 to move inboard. As the caliper 114 moves inboard it moves the outboard friction element towards the rotor 116 clamping the rotor 116 between the outboard and the inboard friction elements 122 and thereby effecting braking by frictionally inhibiting rotation of the rotor 116.
In use, the disc brake is mounted to an axle of a vehicle. This may be achieved by connecting the carrier to a mount on the axle, typically via a bracket welded to the axle. Bolts arranged parallel to an axis of rotation of the rotor secure the carrier to the mount.
Alternatively, for example where an axle has a flange for connection to a drum brake, the carrier is generally attached to a separate mount, often referred to as an adapter plate, and the separate mount is connected to the flange. Axial mounting may result in difficulty in accessing bolts to assemble/disassemble the brake, as well as increase the weight of the brake due to the material doubling at the interface between the mount and carrier. Accordingly, tangential mounting may be used, i.e. the carrier is mounted to the mount via fasteners (e.g. bolts) that extend in a direction tangential to the rotor and substantially perpendicular to the axis of rotation of the rotor.
Features of the carrier and mount generally enable the carrier to be accurately mounted to the axle in a direction A parallel to an axis of rotation of the rotor 116. However, there may be difficulties aligning the carrier with respect to a rotor of a disc brake. Referring to FIG. 2, misalignment of the carrier can result in the rotor 116 and friction element 122 being misaligned, such that the friction element 122 is spaced from the rotor by a greater distance 121 at one side of the friction element than at an opposite side of the friction element. This misalignment can result in taper (i.e. uneven) pad wear and/or non-uniform loading of the caliper mechanism and components. This may be particularly problematic in brakes where bolts secure the carrier to the mount in a tangential or chordal direction (so-called tangential mount carriers), as there may be no overlap of faces of the carrier and mount in the axial direction to aid alignment. This problem is particularly problematic in heavy vehicles rather than lighter vehicles because the larger dimensions of heavy vehicle brakes tend to amplify the effects of any misalignment.